A. J. F. Hayes, A. Gilchrist, C. R. Myers, T. C. Ralph
We present a scheme which offers a significant reduction in the resources required to implement linear optics quantum computing. The scheme is a variation of the proposal of Knill, Laflamme, and Milburn, and makes use of an incremental approach to the error encoding to boost probability of success.
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Quantum Algorithm for Binary Vector Encoding and Retrieval Utilizing the Permutation Trick
提出基于置换技巧的量子存储与检索算法，比Ventura-Martinez方法更简单，且检索步数从√n降至√k，实现更高效的二进制向量处理。
Utilizing encoding time as a resource to enhance quantum sensing by probe qubit dephasing
研究了杂质量子比特浸没在准二维偶极玻色-爱因斯坦凝聚体中的系统，通过探测量子比特退相干估计偶极-偶极相互作用强度，发现长编码时间可增强传感精度，为提高退相干量子比特的传感精度提供新途径。
Linear-optical approach to encoding qubits into harmonic-oscillator modes via quantum walks
本文提出以猫态为量子硬币、借助 MZI 和后选择实现量子行走编码的线性光学方案，可在现有光学与超导电路平台上高保真制备近似 GKP 网格态量子比特。
We have devised an optical scheme for the recently proposed protocol for encoding two qubits into one qutrit. In this protocol, Alice encodes an arbitrary pure product state of two qubits into a state of one qutrit. Bob can then restore error-free any of the two encoded qubit states but not both of them simultaneously. We have successfully realized this scheme experimentally using spatial-mode encoding. Each qubit (qutrit) was represented by a single photon that could propagate through two (three) separate fibers. We theoretically propose two generalizations of the original protocol. We have f…
Both discrete and continuous systems can be used to encode quantum information. Most quantum computation schemes propose encoding qubits in two-level systems, such as a two-level atom or an electron spin. Others exploit the use of an infinite-dimensional system, such as a harmonic oscillator. In "Encoding a qubit in an oscillator" [Phys. Rev. A 64 012310 (2001)], Gottesman, Kitaev, and Preskill (GKP) combined these approaches when they proposed a fault-tolerant quantum computation scheme in which a qubit is encoded in the continuous position and momentum degrees of freedom of an oscillator. On…
We present a new optical scheme for BB84 protocol quantum key distribution (QKD). The proposed setup consists of a compact all-fiber polarization encoding optical scheme based on LiNbO3 phase modulators, single laser source and two single-photon detectors. Optical scheme consists of standard telecommunication components and is suitable for both fiber and free-space quantum communication channels. Low losses (~2dB) in Bob's device increase both the key generation rate and distance limit. A new technique for solving polarization mode dispersion (PMD) issue in LiNbO3 is implemented, allowing two …
We suggest an efficient scheme for quantum computation with linear optical elements utilizing "linked" photon states. The linked states are designed according to the particular quantum circuit one wishes to process. Once a linked-state has been successfully prepared, the computation is pursued deterministically by a sequence of teleportation steps. The present scheme enables a significant reduction of the average number of elementary gates per logical gate to about 20-30 CZ_{9/16} gates.
A real-time polarization control system employing two nonorthogonal reference signals multiplexed in either time or wavelength with the data signal is presented. It is shown, theoretically and experimentally, that complete control of multiple polarization states can be attained employing polarization controllers in closed-loop configuration. Experimental results show that negligible added penalties, corresponding to an average added optical Quantum Bit Error Rate of 0.044%, can be achieved with response times smaller than 10 ms, without significant introduction of noise counts in the quantum c…
We show that the KLM scheme [Knill, Laflamme and Milburn, Nature {\bf 409}, 46] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of err…
Light is an irreplaceable means of communication among various quantum information processing and storage devices. Due to their different physical nature, some of these devices couple more strongly to discrete, and some to continuous degrees of freedom of a quantum optical wave. It is therefore desirable to develop a technological capability to interconvert quantum information encoded in these degrees of freedom. Here we generate and characterize an entangled state between a dual-rail (polarization-encoded) single-photon qubit and a qubit encoded as a superposition of opposite-amplitude cohere…
Today's most widely used method of encoding quantum information in optical qubits is the dual-rail basis, often carried out through the polarisation of a single photon. On the other hand, many stationary carriers of quantum information - such as atoms - couple to light via the single-rail encoding in which the qubit is encoded in the number of photons. As such, interconversion between the two encodings is paramount in order to achieve cohesive quantum networks. In this paper, we demonstrate this by generating an entangled resource between the two encodings and using it to teleport a dual-rail …
Transfer of quantum information between physical systems of a different nature is a central matter in quantum technologies. Particularly challenging is the transfer between discrete- and continuous degrees of freedom of various harmonic oscillator systems. Here we implement a protocol for teleporting a continuous-variable optical qubit, encoded by means of coherent states, onto a discrete-variable, single-rail qubit - a superposition of the vacuum- and single-photon optical states - via a hybrid entangled resource. We test our protocol on coherent states of different phases and obtain the tele…
A scheme for the implementation of the cluster state model of quantum computing in optical fibers, which enables the feedforward feature, is proposed. This scheme uses the time-bin encoding of qubits. Following previously suggested methods of applying arbitrary one-qubit gates in optical fibers, two different ways for the realization of fusion gate types I and II for cluster production are proposed: a fully time-bin based encoding scheme and a combination of time-bin and polarization based encoding scheme. Also the methods of measurement in any desired bases for the purpose of the processing o…
Parallelizable Synthesis of Arbitrary Single-Qubit Gates with Linear Optics and Time-Frequency Encoding
本文提出在时间仓和频率仓编码下利用光谱线性光学量子计算平台精确综合任意单量子比特门的方法，并系统分析了并行实现多量子比特门的资源需求与性能，展示了其在量子计量与层析成像中的应用潜力。
Unified framework for bosonic quantum information encoding, resources and universality from superselection rules
本文提出基于超选择规则的统一框架，统一了玻色子编码、资源和通用性，强调了高斯与非高斯资源及模式与状态的相互作用。
A linear optics network is a multimode interferometer system, where indistinguishable photon inputs can create nonclassical interference that can not be simulated with classical computers. Such nonclassical interference implies the existence of entanglement among its subsystems, if we divide its modes into different parties. Entanglement in such systems is naturally encoded in multi-rail (multi-mode) quantum registers. For bipartite entanglement, a generation and detection scheme with multi-rail encoding has been theoretically proposed [NJP 19(10):103032, 2017] and experimentally realized [Opt…
We propose two types of quantum dense coding communication networks with optical continuous variables, in which a quadripartite entangled state of the optical field with totally three-party correlations of quadrature amplitudes is utilized. In the networks, the exchange of information between any two participants can be manipulated by one or two of the remaining participants. The channel capacities for a variety of communication protocols are numerically calculated. Due to the fact that the quadripartite entangled states applied in the communication systems have been successfully prepared alre…
Quantum-optimal information encoding using noisy passive linear optics
本研究针对无需外部能源的光学量子信道，通过优化Holevo信息发现，均匀分布相移参数及有限个衰减值可实现最优信息编码，并适用于热噪声下的量子读取。
Piecewise Polynomial Tensor Network Quantum Feature Encoding
本文提出分段多项式张量网络量子特征编码（PPTNQFE），利用低秩张量网络将连续变量空间局部化嵌入量子电路，以支持偏微分方程求解和含跳跃间断函数的回归建模。
Error-detection and correction are necessary prerequisites for any scalable quantum computing architecture. Given the inevitability of unwanted physical noise in quantum systems and the propensity for errors to spread as computations proceed, computational outcomes can become substantially corrupted. This observation applies regardless of the choice of physical implementation. In the context of photonic quantum information processing, there has recently been much interest in passive linear optics quantum computing, which includes boson-sampling, as this model eliminates the highly-challenging …
Encoding quantum phase-space with classical wireless microwave constellation
本文提出一个理论框架，利用量子力学网络模型表征天线耦合电光调制器中微波到光学的数字信息映射，实现经典微波星座对量子光学相干态的相空间编码，并探讨了正交分量涨落引发的编码错误及其缓解技术，为桥接经典微波与量子光学链路奠定基础。
The time-frequency degree of freedom is a powerful resource for implementing high-dimensional quantum information processing. In particular, field-orthogonal pulsed temporal modes offer a flexible framework compatible with both long-distance fibre networks and integrated waveguide devices. In order for this architecture to be fully utilised, techniques to reliably generate diverse quantum states of light and accurately measure complex temporal waveforms must be developed. To this end, nonlinear processes mediated by spectrally shaped pump pulses in group-velocity engineered waveguides and crys…
Optical phase encoding in pulsed approach to reservoir computing
本文提出在飞秒激光脉冲的光学相位上编码数据，并采用零差探测读取振幅与相位组合，以光子方式实现储备池计算，且在 NARMA 任务和激光动力学预测中完成数值与实验验证。
Quantum reservoir computing using the stabilizer formalism for encoding classical data
本文提出基于稳定子陪集子空间的量子储备池编码解码方法，并通过逻辑斯蒂与埃农映射时间序列验证了性能随训练数据长度提升。
Floodlight quantum key distribution (FL-QKD) uses binary phase-shift keying (BPSK) of multiple optical modes to achieve Gbps secret-key rates (SKRs) at metropolitan-area distances. We show that FL-QKD's SKR can be doubled by using 32-ary PSK.
The Gottesman-Kitaev-Preskill (GKP) encoding of a qubit within an oscillator provides a number of advantages when used in a fault-tolerant architecture for quantum computing, most notably that Gaussian operations suffice to implement all single- and two-qubit Clifford gates. The main drawback of the encoding is that the logical states themselves are challenging to produce. Here we present a method for generating optical GKP-encoded qubits by coupling an atomic ensemble to a squeezed state of light. Particular outcomes of a subsequent spin measurement of the ensemble herald successful generatio…
We describe a scheme for the encoding and manipulation of single photon qubits in radio frequency sideband modes using standard optical elements.
Here, we study the capacity of a quantum channel, assuming linear optical encoding, as a function of available photons and optical modes. First, we observe that substantial improvement is made possible by not restricting ourselves to a rail-encoded qubit basis. Then, we derive an analytic formula for general channel capacity and show that this capacity is achieved without requiring the use of entangling operations typically required for scalable universal quantum computation, e.g. KLM measurement-assisted transformations. As an example, we provide an explicit encoding scheme using the resource…
In quantum communications, quantum states are employed for the transmission of information between remote parties. This usually requires sharing knowledge of the measurement bases through a classical public channel in the sifting phase of the protocol. Here, we demonstrate a quantum communication scheme where the information on the bases is shared "non-classically", by encoding this information in the same photons used for carrying the data. This enhanced capability is achieved by exploiting the localization of the photonic wave function, observed when the photons are prepared and measured in …
Quantum Steganography via Coherent and Fock State Encoding in an Optical Medium
该研究提出在光学信道中利用 Fock 态和相干态、并以热噪声为伪装的量子隐写通信方案，给出全能窃听者条件下的效率界及无噪声信道的编码与纠错方法。
The linear optical creation of Gaussian cluster states, a potential resource for universal quantum computation, is investigated. We show that for any Gaussian cluster state, the canonical generation scheme in terms of QND-type interactions, can be entirely replaced by off-line squeezers and beam splitters. Moreover, we find that, in terms of squeezing resources, the canonical states are rather wasteful and we propose a systematic way to create cheaper states. As an application, we consider Gaussian cluster computation in multiple-rail encoding. This encoding may reduce errors due to finite squ…
We present methods which allow orders of magnitude increase in the number of modes in linear optics experiments by moving from spatial encoding to temporal encoding and using dispersion. This enables significant practical advantages for linear quantum optics and Boson Sampling experiments. Passing consecutively heralded photons through time-independent dispersion and measuring the output time of the photons is equivalent to a Boson Sampling experiment for which no efficient classical algorithm is reported, to our knowledge. With time-dependent dispersion, it is possible to implement arbitrary …
On-chip Time-bin to Path Qubit Encoding Converter via Thin Film Lithium Niobate Photonics Chip
本文提出了一种基于薄膜铌酸锂光子芯片的片上时间分量到路径量子比特编码转换器，通过实验验证其高保真度转换性能，为量子网络中的信息传输与处理提供基础组件。
We use a combination of analytical and numerical techniques to calculate the noise threshold and resource requirements for a linear optical quantum computing scheme based on parity-state encoding. Parity-state encoding is used at the lowest level of code concatenation in order to efficiently correct errors arising from the inherent nondeterminism of two-qubit linear-optical gates. When combined with teleported error-correction (using either a Steane or Golay code) at higher levels of concatenation, the parity-state scheme is found to achieve a saving of approximately three orders of magnitude …
We establish the fundamental limit of communication capacity within Gaussian schemes under phase-insensitive Gaussian channels, which employ multimode Gaussian states for encoding and collective Gaussian operations and measurements for decoding. We prove that this Gaussian capacity is additive, i.e., its upper bound occurs with separable encoding and separable receivers so that a single-mode communication suffices to achieve the largest capacity under Gaussian schemes. This rigorously characterizes the gap between the ultimate Holevo capacity and the capacity within Gaussian communication, sho…
Passive state preparation for quantum key distribution with phase encoding
本研究针对相位编码量子密钥分发场景，提出基于增益开关激光器脉冲相位差测量的被动态制备方法，通过仿真验证了该方法的有效性，为量子密钥分发的态制备提供了新的被动实现方案。
Despite extensive research efforts, few quantum algorithms for classical optimization demonstrate realizable quantum advantage. The utility of many quantum algorithms is limited by high requisite circuit depth and nonconvex optimization landscapes. We tackle these challenges by introducing a new variational quantum algorithm that benefits from two innovations: multi-basis graph encodings and nonlinear activation functions. Our technique results in increased optimization performance, a factor of two increase in effective quantum resources, and a quadratic reduction in measurement complexity. Wh…
We propose a linear-optical implementation of a hyperentanglement-assisted quantum error-correcting code. The code is hyperentanglement-assisted because the shared entanglement resource is a photonic state hyperentangled in polarization and orbital angular momentum. It is possible to encode, decode, and diagnose channel errors using linear-optical techniques. The code corrects for polarization "flip" errors and is thus suitable only for a proof-of-principle experiment. The encoding and decoding circuits use a Knill-Laflamme-Milburn-like scheme for transforming polarization and orbital angular …
The probabilistic nature of single-photon sources and photon-photon interactions encourages encoding as much quantum information as possible in every photon for the purpose of photonic quantum information processing. Here, by encoding high-dimensional units of information (qudits) in time and frequency degrees of freedom using on-chip sources, we report deterministic two-qudit gates in a single photon with fidelities exceeding 0.90 in the computational basis. Constructing a two-qudit modulo SUM gate, we generate and measure a single-photon state with non-separability between time and frequency…
Quantum circuit simulation of linear optics using fermion to qubit encoding
提出一种结合玻色子-费米子对应和费米子到量子比特编码的数字量子模拟协议，用于玻色子线性散射，并通过IBM Quantum和IonQ云服务验证了Hong-Ou-Mandel凹陷电路。
Generalized Number-Phase Lattice Encoding of a Bosonic Mode for Quantum Error Correction
本文针对玻色子系统量子纠错的对称性利用局限，提出基于数相变量相空间对称性的统一编码框架，构建数相格点码（含矩形、斜形、菱形），其斜形和菱形码通过数相涡旋效应高效纠错，在抗退相干噪声上优于传统正交码，为容错计算和通信扩展提供新方案。
Fermihedral: On the Optimal Compilation for Fermion-to-Qubit Encoding
本文提出编译器框架Fermihedral，利用Pauli代数将费米子到量子比特编码转化为布尔可满足性问题求解，并设计近似策略应对大规模场景，大幅降低电路成本并提升真实量子设备上的模拟精度。
Quantum simulation of wave optics in weakly inhomogeneous media using block-encoding
本文提出一种量子算法，用于模拟光场在弱非均匀介质中的传播。通过将非均匀介质中的波动方程转化为时间依赖的薛定谔方程，利用块编码高效模拟多种光学装置。通过模拟高斯光束通过有限厚度透镜的传播，展示球面像差。
We propose a scheme which encodes information in both the longitudinal and spatial transverse phases of a continuous-wave optical beam. A split detector-based interferometric scheme is then introduced to optimally detect both encoded phase signals. In contrast to present-day optical storage devices, our phase coding scheme has an information storage capacity which scales with the power of the read-out optical beam. We analyse the maximum number of encoding possibilities at the shot noise limit. In addition, we show that using squeezed light, the shot noise limit can be overcome and the number …
A heavy focus for optical quantum computing is the introduction of error-correction, and the minimisation of resource requirements. We detail a complete encoding and manipulation scheme designed for linear optics quantum computing, incorporating scalable operations and loss-tolerant architecture.
We propose a scheme for the generation of hybrid states entangling a single-photon time-bin qubit with a coherent-state qubit encoded on phases. Compared to other reported solutions, time-bin encoding makes hybrid entanglement particularly well adapted to applications involving long-distance propagation in optical fibers. This makes our proposal a promising resource for future out-of-the-laboratory quantum communication. In this perspective, we analyze our scheme by taking into account realistic experimental resources and discuss the impact of their imperfections on the quality of the obtained…
Quantum algorithm for solving high-dimensional linear stochastic differential equations via amplitude encoding of the noise term
本文提出两种量子算法，通过幅度编码解决高维随机微分方程，利用伪随机数生成器实现噪声项编码，提升维度效率。
An energy-time entanglement-based dispersive optics quantum key distribution (DO-QKD) is demonstrated experimentally over optical fibers of 20 km. In the experiment, the telecom band energy-time entangled photon pairs are generated through spontaneous four wave mixing in a silicon waveguide. The arrival time of photons are registered for key generating and security test. High dimensional encoding in the arrival time of photons is used to increase the information per coincidence of photon pairs. The bin sifting process is optimized by a three level structure, which significantly reduces the raw…
Integrated photonic technologies applied to quantum optics have recently enabled a wealth of breakthrough experiments in several quantum information areas. Path encoding was initially used to demonstrate operations on single or multiple qubits. However, a polarization encoding approach is often simpler and more effective. Two-qubits integrated logic gates as well as complex interferometric structures have been successfully demonstrated exploiting polarization encoding in femtosecond-laser-written photonic circuits. Still, integrated devices performing single-qubit rotations are missing. Here w…
The light's image is the primary source of information carrier in nature. Indeed, a single photon's image possesses a vast information capacity that can be harnessed for quantum information processing. Our scheme for implementing quantum information processing via universal multiport processors employs a class of quantum Fourier optical systems composed of spatial phase modulators and 4f-processors with phase-only pupils having a characteristic periodicity that reduces the number of optical resources quadratically as compared to other conventional path encoding techniques. In particular, this …
Entanglement is the basic building block of linear optical quantum computation, and as such understanding how to generate it in detail is of great importance for optical architectures. We prove that Bell states cannot be generated using only 3 photons in the dual-rail encoding, and give strong numerical evidence for the optimality of the existing 4 photon schemes. In a setup with a single photon in each input mode, we find a fundamental limit on the possible entanglement between a single mode Alice and arbitrary Bob. We investigate and compare other setups aimed at characterizing entanglement …
We propose an efficient phase-encoding quantum secret key generation scheme with heralded narrow-band single photons. The key information is carried by the phase modulation directly on the single-photon temporal waveform without using any passive beam splitters or optical switches. We show that, when the technique is applied to the conventional fiber-based phase-encoding BB84 and differential phase shift (DPS) quantum key distribution schemes, the key generation efficiencies can be improved by a factor of 2 and 3, respectively. For N(>3)-period DPS systems, the key generation efficiency can be…
End-to-End Quantum Key Distribution Across Hybrid Fiber and Free-Space Links with All-Optical Encoding Conversion
研究如何实现跨混合光纤和自由空间链路的端到端量子密钥分发，利用全光编码转换执行诱骗态BB84协议，在不同大气条件下实现连续安全密钥生成，验证光子级操作，确立编码转换为实用接口，为量子网络应用提供构建模块。
A comparison on constrain encoding methods for quantum approximate optimization algorithm
针对量子近似优化算法（QAOA）求解约束满足问题的需求，对比了三种线性约束编码策略，以背包问题为案例评估其效率与有效性，为不同场景的方法选型提供参考。
We introduce an electro-optical arrangement that is able to produce time-bin encoded symbols with the decoy state method over a standard optical fiber in the C-band telecom window. The device consists of a specifically designed pulse pattern generator for pulse production, a field-programmable gate array that controls timing and synchronization. The electrical pulse output drive a sequence of intensity modulators acting on a continuous laser that deliver bursts of weak optical pulse pairs of discrete intensity values. Such transmitter allows for the generation of all the quantum states needed …
A theoretical study of subcarrier-wave quantum key distribution system integration with an optical transport network utilizing dense wavelength division multiplexing
本文理论研究了DWDM光传输网络中SCW QKD的性能，考虑拉曼散射、四波混频等噪声，计算了QBER和安全密钥率，发现1310 nm波长优于C波段。
Unwrapping photonic reservoirs: enhanced expressivity via random Fourier encoding over stretched domains
本文提出一种散射辅助的光子储备池编码方案，通过将输入相位多次缠绕超出自然周期，利用随机合成频率间的非线性干涉生成丰富特征空间，显著提升了系统在原本无法实现的回归与分类任务中的预测性能。
Block Encodings of Discrete Subgroups on Quantum Computer
本研究提出一种适用于一般离散群的量子比特块编码方法，构建了$\n\bT$及首次实现$\n\bI$群的基本量子门，给出胶子粘度提取的资源估算，并在$\texttt{Baiwang}$量子计算机上完成两类逆门的保真度基准测试。
Programmable Photonic Quantum Circuits with Ultrafast Time-bin Encoding
提出一种利用超快时间bin编码的量子信息处理平台，通过两项实验验证了其可编程性（实现362种酉变换）与可扩展性（达36个光学模式），保真度超97%且相位稳定数天。
In this work the novel usage of a physically unclonable function composed of a network of Mach-Zehnder interferometers for authentication tasks is described. The physically unclonable function hardware is completely reconfigurable, allowing for a large number of seemingly independent devices to be utilized, thus imitating a large array of single-response physically unclonable functions. It is proposed that any reconfigurable array of Mach-Zehnder interferometers can be used as an authentication mechanism, not only for physical objects, but for information transmitted both classically and quant…
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